Start-up circuit for an output driver

BACKGROUND

p-0002Generally, an output driver comprises a metal oxide semiconductor (MOS) transistor and is associated with a delayed response time when the MOS transistor or MOS driver is turned on. For example, the MOS transistor is delayed at least due to a variation in at least one of process, voltage, or temperature (PVT) associated with the output driver. Additionally, the MOS transistor is delayed at least because a gate of the MOS transistor or MOS driver requires time to pull the gate of the MOS to a turn-on voltage. In some scenarios the delay results in a disproportionate rise fall ratio for the output driver. For example, if the delay is associated with a pull down transistor, such as the MOS transistor connected to a pad, a rising time is less than a falling time for the output driver, thus leading to the disproportionate rise fall ratio.

SUMMARY

p-0003This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to be an extensive overview of the claimed subject matter, identify key factors or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

p-0004One or more techniques and systems for starting an output driver and an associated start-up circuit for operating the output driver are provided herein. In some embodiments, a voltage provider charges a charge store to a pre-turn-on voltage. The charge store is connected to an output driver such that a metal oxide semiconductor (MOS) transistor or a MOS driver of the output driver receives the charge of the charge store at the pre-turn-on voltage. In some embodiments, the MOS driver is configured to control a voltage of a pad based on the connection from the charge store to the output driver.

p-0005The following description and annexed drawings set forth certain illustrative aspects and implementations. These are indicative of but a few of the various ways in which one or more aspects are employed. Other aspects, advantages, or novel features of the disclosure will become apparent from the following detailed description when considered in conjunction with the annexed drawings.

DESCRIPTION OF THE DRAWINGS

p-0006Aspects of the disclosure are understood from the following detailed description when read with the accompanying drawings. It will be appreciated that elements, structures, etc. of the drawings are not necessarily drawn to scale. Accordingly, the dimensions of the same may be arbitrarily increased or reduced for clarity of discussion, for example.

p-0007<figref idrefs="DRAWINGS">FIG. 1</figref> is a schematic diagram of an example start-up circuit for operating an output driver, according to some embodiments.

p-0008<figref idrefs="DRAWINGS">FIG. 2</figref> is a schematic diagram of an example start-up circuit for operating an output driver, according to some embodiments.

p-0009<figref idrefs="DRAWINGS">FIG. 3</figref> is a schematic diagram of an example start-up circuit for operating an output driver, according to some embodiments.

p-0010<figref idrefs="DRAWINGS">FIG. 4</figref> is a schematic diagram of an example voltage provider of a start-up circuit, according to some embodiments.

p-0011<figref idrefs="DRAWINGS">FIG. 5</figref> is a schematic diagram of an example charge store of a start-up circuit, according to some embodiments.

p-0012<figref idrefs="DRAWINGS">FIG. 6</figref> is a schematic diagram of an example output driver of a start-up circuit, according to some embodiments.

p-0013<figref idrefs="DRAWINGS">FIG. 7</figref> is a flow diagram of an example method for starting an output driver, according to some embodiments.

p-0014<figref idrefs="DRAWINGS">FIG. 8</figref> is a schematic diagram of an example start-up circuit for operating an output driver, according to some embodiments.

p-0015<figref idrefs="DRAWINGS">FIG. 9</figref> is a schematic diagram of an example start-up circuit for operating an output driver, according to some embodiments.

p-0016<figref idrefs="DRAWINGS">FIG. 10</figref> is a schematic diagram of an example start-up circuit for operating an output driver, according to some embodiments.

DETAILED DESCRIPTION

p-0017The claimed subject matter is now described with reference to the drawings, wherein like reference numerals are generally used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the claimed subject matter. It is evident, however, that the claimed subject matter may be practiced without these specific details. In other instances, structures and devices are illustrated in block diagram form in order to facilitate describing the claimed subject matter.

p-0018<figref idrefs="DRAWINGS">FIG. 1</figref> is a schematic diagram of an example start-up circuit <b>100</b> for operating an output driver, according to some embodiments. For example, the start-up circuit <b>100</b> comprises a voltage provider <b>110</b>, a charge store <b>120</b>, an output driver <b>130</b>, and pad <b>108</b>. In some embodiments, the start-up circuit <b>100</b> comprises a first control switch <b>144</b>, a second control switch <b>142</b>, and a third control switch <b>146</b>. In some embodiments, the voltage provider <b>110</b> is connected to ground <b>106</b> and the second control switch <b>142</b>. Additionally, the charge store <b>120</b> is connected to ground <b>106</b>, the first control switch <b>144</b>, and the second control switch <b>142</b>. In some embodiments, the output driver <b>130</b> is connected to ground <b>106</b>, pad <b>108</b>, the first control switch <b>144</b>, and the third control switch <b>146</b>.

p-0019In some embodiments, the second control switch <b>142</b> is configured to control a second connection between the voltage provider <b>110</b> and the charge store <b>120</b>. That is, the second control switch <b>142</b> connects or disconnects the voltage provider <b>110</b> from the charge store <b>120</b> when closed or opened, respectively. In some embodiments, the voltage provider <b>110</b> is configured to charge the charge store <b>120</b> to a pre-turn-on voltage when the second control switch <b>142</b> is closed. Additionally, it will be appreciated that the second control switch <b>142</b> and the third control switch <b>146</b> are configured to open when the first control switch <b>144</b> is closed and vice versa, in some embodiments. Therefore, when the voltage provider <b>110</b> is connected to the charge store <b>120</b> via the second control switch <b>142</b>, the output driver <b>130</b> is not connected to the charge store <b>120</b> at least because the first control switch <b>144</b> is open. Accordingly, the first control switch <b>144</b> is configured to control a first connection between the charge store <b>120</b> and the output driver <b>130</b>. That is, the first control switch <b>144</b> connects or disconnects the charge store <b>120</b> from the output driver <b>130</b>. For example, when the first control switch <b>144</b> is open, the charge store <b>120</b> is disconnected from the output driver <b>130</b>. In another example, when the first control switch <b>144</b> is closed, the charge store <b>120</b> is connected to the output driver <b>130</b>. In some embodiments, the first control switch <b>144</b> is configured to enable charge sharing between the charge store <b>120</b> and the output driver <b>130</b>. For example, when charge sharing is enabled, such as when the first control switch <b>144</b> is closed, a discharged voltage is provided to the output driver <b>130</b> from the charge store <b>120</b>. It will be appreciated that the charge store <b>120</b> is charged to a pre-turn-on voltage different than the discharged voltage in some embodiments. In some embodiments, the charge store <b>120</b> is a structure configured to store a charge, such as a capacitor, for example. In other embodiments, the charge store <b>120</b> is a circuit configured to store a charge, such as an electrostatic discharge (ESD) circuit, for example. In some embodiments, the charge store <b>120</b> is a parasitic capacitance.

p-0020In some embodiments, the voltage provider <b>110</b> is configured to charge the charge store <b>120</b> to a pre-turn-on voltage via the second control switch <b>142</b> at a first time. Additionally, at the first time, the first control switch <b>144</b> is open and the third control switch <b>146</b> is closed such that the voltage provider <b>110</b> and the charge store <b>120</b> forms a first circuit and the output driver forms a second circuit not connected to the first circuit. Accordingly, after the first time has passed, the charge store <b>120</b> is charged to the pre-turn-on voltage by the voltage provider <b>110</b>. At a second time, the second control switch <b>142</b> and the third control switch <b>146</b> are opened, and the first control switch <b>144</b> is closed. Therefore, the voltage provider <b>110</b> forms a third circuit, and the charge store <b>120</b> and the output driver <b>130</b> forms a fourth circuit not connected to the third circuit. At the second time, the first control switch <b>144</b> connects the charge store <b>120</b> to the output driver <b>130</b> and enables the charge store <b>120</b> to provide the pre-turn-on voltage to the output driver <b>130</b>. For example, the charge store <b>120</b> is configured to discharge a stored voltage of the charge store <b>120</b>, such as the pre-turn-on voltage, to the output driver <b>130</b> via the first control switch <b>144</b>. For example, the charge store <b>120</b> is configured to discharge a stored charge to the output driver <b>130</b> through the first control switch <b>144</b>, thus applying the stored charge to the output driver <b>130</b>. Accordingly, a voltage level of the output driver <b>130</b> will rise to a pre-turn-on voltage. In this way, the output driver <b>130</b> is activated such that a response time between the discharge of the charge store <b>120</b> and activation of the output driver <b>130</b> is mitigated. Additionally, there is substantially no start-up current associated with discharging the charge store <b>120</b> to the output driver <b>130</b>, thus mitigating process, voltage, or temperature (PVT) variations associated with starting the output driver <b>130</b>. In addition to mitigating a delay associated with a response time for the output driver <b>130</b>, a rise fall ratio is controlled at least because a smaller delay generally results in tighter falling times for a voltage level associated with a pad of the output driver <b>130</b>, for example.

p-0021In some embodiments, the third control switch <b>146</b> is configured to control a third connection between a portion of the output driver <b>130</b> and ground <b>106</b>. That is, the third control switch <b>146</b> connects or disconnects the portion of the output driver <b>130</b> to ground <b>106</b>. In some embodiments, the third control switch <b>146</b> is configured to control the third connection between a third gate of a third MOS transistor of the output driver <b>130</b> and ground <b>106</b>. Additionally, the third control switch <b>146</b> is connected to the first control switch <b>144</b>. In some embodiments, the third control switch <b>146</b> is configured to control the third connection based on logic of the second control switch <b>142</b>.

p-0022<figref idrefs="DRAWINGS">FIG. 2</figref> is a schematic diagram of an example start-up circuit <b>200</b> for operating an output driver, according to some embodiments. It will be appreciated that in some embodiments, the start-up circuit <b>200</b> of <figref idrefs="DRAWINGS">FIG. 2</figref> is the start-up circuit <b>100</b> of <figref idrefs="DRAWINGS">FIG. 1</figref> where the first control switch <b>144</b> is open, the second control switch <b>142</b> is closed, and the third control switch <b>146</b> is closed. In some embodiments, the first control switch <b>144</b> is opened, the second control switch <b>142</b> is closed, and the third control switch <b>146</b> is closed at a first time, for example. In this way, a first circuit <b>210</b> and a second circuit <b>220</b> are formed, for example. In some embodiments, the first circuit <b>210</b> comprises the voltage provider <b>110</b> and the charge store <b>120</b>. For example, the voltage provider is connected to the charge store <b>120</b> via a second connection formed by the second control switch <b>142</b>. Additionally, the voltage provider <b>110</b> is connected to ground <b>106</b>. The charge store <b>120</b> is connected to ground <b>106</b>. The first circuit <b>210</b> is thus configured to charge the charge store <b>120</b> based on the voltage provider <b>110</b> and the second control switch <b>142</b>. In some embodiments, the voltage provider <b>110</b> is configured to charge the charge store <b>120</b> to a pre-turn-on voltage. The second circuit <b>220</b> is configured to connect a portion of the output driver <b>130</b> to ground <b>106</b> via a third control switch <b>146</b>. It will be appreciated that the third control switch <b>146</b> is closed at the first time. Additionally, the output driver <b>130</b> is connected to pad <b>108</b> and ground <b>106</b>. In some embodiments, the output driver <b>130</b> waits for the charge store <b>120</b> to reach the pre-turn-on voltage during the first time.

p-0023<figref idrefs="DRAWINGS">FIG. 3</figref> is a schematic diagram of an example start-up circuit <b>300</b> for operating an output driver, according to some embodiments. It will be appreciated that in some embodiments, the start-up circuit <b>300</b> of <figref idrefs="DRAWINGS">FIG. 3</figref> is the start-up circuit <b>100</b> of <figref idrefs="DRAWINGS">FIG. 1</figref> where the first control switch <b>144</b> is closed, the second control switch <b>142</b> is open, and the third control switch <b>146</b> is open. In some embodiments, the first control switch <b>144</b> is closed, the second control switch <b>142</b> is opened, and the third control switch <b>146</b> is opened at a second time. In some examples, the second time is at a time after the first time associated with the start-up circuit <b>200</b> of <figref idrefs="DRAWINGS">FIG. 2</figref>. In this way, a third circuit <b>310</b> and a fourth circuit <b>320</b> are formed, for example. In some embodiments, the third circuit <b>310</b> comprises the voltage provider <b>110</b>. In some embodiments, the voltage provider <b>110</b> is connected to ground <b>106</b>. The fourth circuit <b>320</b> comprises the charge store <b>120</b> and the output driver <b>130</b>. In some embodiments, the first control switch <b>144</b> is closed at the second time, thus connecting the charge store <b>120</b> and the output driver <b>130</b>. Additionally, the output driver <b>130</b> is connected to pad <b>108</b> and ground <b>106</b>. In some embodiments, the charge store <b>120</b> discharges a stored voltage to the output driver <b>130</b>. For example, when the first control switch <b>144</b> is closed, the stored voltage of the charge store <b>120</b> activates the output driver <b>130</b> in a manner that does not require a pull up or pull down transistor to bias a gate of a driver transistor for the output driver <b>130</b>. In other words, the stored voltage of the charge store <b>120</b> enables a rapid activation of the output driver <b>130</b>, thus mitigating a response time associated with the activating the output driver <b>130</b>. For example, the driver transistor is configured to enter a saturation region quickly, such as within 1 ns, when the stored voltage of the charge store <b>120</b> is discharged to the driver transistor.

p-0024<figref idrefs="DRAWINGS">FIG. 4</figref> is a schematic diagram of an example voltage provider <b>110</b> of a start-up circuit, according to some embodiments. In some embodiments, the voltage provider <b>110</b> comprises a first current source <b>430</b>, a first metal oxide silicon (MOS) transistor <b>410</b>, a second MOS transistor <b>420</b>, and a second control switch <b>142</b>. In some embodiments, the first current source <b>430</b> is configured to provide an output drive current. For example, the first current source <b>430</b> is connected to the second control switch <b>142</b>, a first gate <b>412</b> of the first MOS transistor <b>410</b>, and a first drain <b>416</b> of the first MOS transistor <b>410</b>. In some embodiments, a first source <b>414</b> of the first MOS transistor <b>410</b> is connected to a second gate <b>422</b> of the second MOS transistor <b>420</b> and a second drain <b>426</b> of the second MOS transistor <b>420</b>. For example, in some embodiments, two or more MOS transistors are cascaded to provide a pre-turn-on voltage. A second source <b>424</b> of the second MOS transistor <b>420</b> is connected to ground <b>106</b>. Additionally, the first gate <b>412</b> of the first MOS transistor <b>410</b> is connected to the first drain <b>416</b> of the first MOS transistor <b>410</b>. In this way, the first MOS transistor <b>410</b> comprises a diode configuration. Similarly, the second gate <b>422</b> of the second MOS transistor <b>420</b> is connected to the second drain <b>426</b> of the second MOS transistor <b>420</b>. In this way, the second MOS transistor <b>420</b> comprises a diode configuration. Accordingly, the first MOS transistor <b>410</b> or the second MOS transistor is configured to operate as a diode, in some examples. In some embodiments, the pre-turn-on voltage is associated with a turn on voltage for a MOS transistor. For example, the first MOS transistor <b>410</b> and the second MOS transistor <b>420</b> are associated with respective turn on voltages (V_on). In some embodiments, the turn on voltage is an operating voltage, for example. For example, if the first MOS transistor <b>410</b> has a turn on voltage of V_onand the second MOS transistor <b>420</b> has a turn on voltage of V_on, a voltage of 2*V_onis required to turn on both the first MOS transistor <b>410</b> and the second MOS transistor <b>420</b>. In some embodiments, the first MOS transistor <b>410</b> acts as a first diode and the second MOS transistor <b>420</b> acts as a second diode, thus enabling current to flow from the first current source <b>430</b> when a voltage greater than 2*V_onis applied, such as at <b>142</b>. Therefore, the first MOS transistor <b>410</b> cascaded with the second MOS transistor <b>420</b> provides a pre-turn-on voltage of 2*V_on. Accordingly, at least one of the first MOS transistor <b>410</b> or the second MOS transistor <b>420</b> is configured to operate at an operating voltage or a turn on voltage (Von) comprising a fraction of the pre-turn-on voltage. For example, when the pre-turn-on voltage is =2*V_on, the first MOS transistor <b>410</b> and the second MOS transistor <b>420</b> are associated with an operating voltage or a turn on voltage of V_on. It will be appreciated that in some embodiments, the pre-turn-on voltage is determined based on a capacitance of the charge store <b>120</b>, an internal capacitance of an output driver <b>130</b>, or a parasitic capacitance associated with a driver transistor for the output driver <b>130</b>. In this way, the pre-turn-on voltage is determined in a precise manner, thus mitigating delays associated with starting the output driver <b>130</b> at least because discharging the charge store <b>120</b> is substantially unaffected by variations across process, voltage, or temperature (PVT). It will be appreciated that the second control switch <b>142</b> is configured to connect the voltage provider <b>110</b> to a charge store <b>120</b>, such as the charge store <b>120</b> of <figref idrefs="DRAWINGS">FIG. 5</figref> at a first time.

p-0025<figref idrefs="DRAWINGS">FIG. 5</figref> is a schematic diagram of an example charge store <b>120</b> of a start-up circuit, according to some embodiments. In some embodiments, the charge store <b>120</b> comprises any capacitance structure configured to store a pre-turn-on charge. For example, charge store <b>120</b> comprises a capacitor <b>510</b> connected to ground <b>106</b>. In other embodiments, the capacitor <b>510</b> is connected to the first control switch <b>144</b> and the second control switch <b>142</b>. It will be appreciated that the first control switch <b>144</b> is configured to connect the charge store to an output driver <b>130</b>, such as the output driver <b>130</b> of <figref idrefs="DRAWINGS">FIG. 6</figref> at a second time.

p-0026<figref idrefs="DRAWINGS">FIG. 6</figref> is a schematic diagram of an example output driver <b>130</b> of a start-up circuit, according to some embodiments. In some embodiments, the output driver <b>130</b> comprises a second current source <b>630</b>, an internal capacitance <b>620</b> associated with the output driver <b>130</b>, a third metal oxide semiconductor (MOS) transistor <b>610</b>, and a parasitic capacitance <b>640</b> associated with the third MOS transistor <b>610</b>. In other embodiments, the output driver comprises at least one of a first control switch <b>144</b> or a third control switch <b>146</b>. For example, the second current source <b>630</b> is connected to the internal capacitance <b>620</b>, a third gate <b>612</b> of the third MOS transistor <b>610</b>, the first control switch <b>144</b>, and the third control switch <b>146</b>. The internal capacitance <b>620</b> is connected to pad <b>108</b> and a third drain <b>616</b> of the third MOS transistor <b>610</b>. In some embodiments, a third source <b>614</b> of the third MOS transistor <b>610</b> is connected to ground <b>106</b>. The parasitic capacitance <b>640</b> is measured across the third gate <b>612</b> and the third source <b>614</b> of the third MOS transistor <b>610</b>, for example. In some embodiments, the third MOS transistor <b>610</b> is a driver for the output driver <b>130</b> configured to drive current in or out of the output driver <b>130</b>. That is the third MOS transistor <b>610</b> is configured to control a voltage level associated with the pad <b>108</b>. In some embodiments, the voltage level associated with the pad <b>108</b> comprises at least one of a logic high or a logic low. Accordingly, the second control switch <b>144</b> and the third control switch <b>146</b> respectively control a second connection and a third connection to facilitate operation of the output driver <b>130</b>. For example, the second control switch <b>144</b> is configured to connect the output driver <b>130</b> to a charge store <b>120</b>, such as the charge store of <figref idrefs="DRAWINGS">FIG. 1</figref>. Additionally, it will be appreciated that the second connection formed by the second control switch <b>144</b> enables the charge store <b>120</b> to discharge directly to the third gate <b>612</b> of the third MOS transistor <b>610</b>. In this way, the third MOS transistor <b>610</b> drives or controls the voltage level associated with the pad <b>108</b>. The third control switch <b>146</b> is configured to connect or disconnect the third gate <b>612</b> of the third MOS transistor <b>610</b> to ground <b>106</b>, thus controlling a pull down operation for the third MOS transistor <b>610</b> and pad <b>108</b>. It will be appreciated that in some embodiments, the third MOS transistor <b>610</b> is an NMOS transistor configured as a pull down transistor. For example, since the third source <b>614</b> of the third MOS transistor <b>610</b> is connected to ground <b>106</b>, the third MOS transistor <b>610</b> is turned on or off based on a voltage level at the third gate <b>612</b>. That is, when a voltage level of the third gate <b>612</b> is a logic low, the third MOS transistor <b>610</b> is off and the pad <b>108</b> is logic high. For another example, when a voltage level of the third gate <b>612</b> is a logic high, the third MOS transistor <b>610</b> is on and the pad <b>108</b> falls from a logic high level to a logic low level, at least because the third MOS transistor <b>610</b> is on and configured to pull down the voltage level of the pad <b>108</b>. In some embodiments, when the third MOS transistor <b>610</b> is on, the pad <b>108</b> is connected to ground <b>106</b>, thus pulling the voltage level associated with the pad <b>108</b> down to a logic low level, for example.

p-0027It will be appreciated that the first control switch <b>144</b> and the third control switch <b>146</b> are operated based on an inverse relationship to control operation of the output driver <b>130</b>. That is, when the first control switch <b>144</b> is open, the third control switch <b>146</b> is closed, and vice versa. In some embodiments, the output driver <b>130</b> is configured to close the third control switch <b>146</b> to short the third connection and open the first control switch <b>144</b> to open the first connection. In other embodiments, the output driver <b>130</b> is configured to open the third control switch <b>146</b> to open the third connection and close the first control switch <b>144</b> to short the first connection. For example, when the third control switch <b>146</b> is closed and the first control switch <b>144</b> is open, the third gate <b>612</b> of the third MOS transistor <b>610</b> is connected to ground <b>106</b> by the third connection formed by the third control switch <b>146</b>. Accordingly, a voltage level at the third gate <b>612</b> is a logic low at least because of the connection to ground <b>106</b> and the third MOS transistor <b>610</b> is off, enabling a voltage level of the pad <b>108</b> to remain at a logic high level. In some embodiments, the first control switch <b>144</b> is open and the third control switch <b>146</b> is closed at a first time.

p-0028For example, when the third control switch <b>146</b> is opened and the first control switch <b>144</b> is closed, the third gate <b>612</b> is connected to a charge store <b>120</b>, such as the charge store of <figref idrefs="DRAWINGS">FIG. 1</figref>. In this way, a third connection is formed by the third control switch <b>146</b>. Accordingly, when this third connection is formed, a voltage level at the third gate <b>612</b> is a logic high at least because of the connection to the charge store <b>120</b>. In some embodiments, the third gate <b>612</b> of the third MOS transistor <b>610</b> is disconnected from the ground <b>106</b> while the charge store <b>120</b> is connected to the output driver <b>130</b>. Therefore, the charge store <b>120</b> discharges a stored voltage, such as a pre-turn-on voltage to the third gate <b>612</b> of the third MOS transistor <b>610</b>, turning the third MOS transistor <b>610</b> on in a rapid and immediate fashion, thus mitigating a delay time associated with a change in the voltage level of the pad <b>108</b>, such as a rising time or a falling time. As mentioned before, when the third MOS transistor <b>610</b> is on, a voltage level of the pad <b>108</b> is pulled down to a logic low level. In this way, the output driver is activated in a precise and immediate fashion, for example. In some embodiments, the third control switch <b>146</b> is opened and the first control switch <b>144</b> is closed at a second time. Additionally, it will be appreciated that the second time is after the first time, for example.

p-0029<figref idrefs="DRAWINGS">FIG. 7</figref> is a flow diagram of an example method <b>700</b> for starting an output driver, according to some embodiments. At <b>702</b>, a charge store is charged to a pre-turn-on voltage. At <b>704</b>, the charge store is connected to an output driver, thus starting the output driver. In some embodiments, charging the charge store comprises connecting or disconnecting a voltage provider to the charge store. In some embodiments, the charge store is the charge store <b>120</b> of <figref idrefs="DRAWINGS">FIG. 5</figref>. Additionally, the pre-turn-on voltage is based on a turn on voltage or operating voltage (V_on) associated with a voltage provider, such as the voltage provider <b>110</b> of <figref idrefs="DRAWINGS">FIG. 4</figref>. In some examples, the voltage provider <b>110</b> is configured to provide a pre-turn-on voltage of 2*V_on. Accordingly, the charge store, such as charge store <b>120</b> stores a charge Q=C*V, where C is a capacitance associated with the charge store <b>120</b>, such as a capacitance of capacitor <b>510</b> of <figref idrefs="DRAWINGS">FIG. 5</figref>. Additionally, V is the voltage stored in the capacitor, and in this example, V=pre-turn-on voltage=2*V_on. Therefore, the charge in the charge store <b>120</b> is Q=C*V=C*2*V_on.

p-0030When the charge store <b>120</b> is connected to an output driver, such as output driver <b>130</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>, a voltage of the charge store <b>120</b> is discharged to the output driver <b>130</b>. In some embodiments, the voltage of the charge store <b>120</b> is discharged to a third gate <b>612</b> of a third MOS transistor <b>610</b>. For example, the discharged voltage is determined such that the discharged voltage=Q/C_{output driver}. In this example, Q=the charge in the charge store, or C*2*V_on. In some embodiments related to <figref idrefs="DRAWINGS">FIG. 6</figref>, C_{output driver}=C+C_int+C_gs. For example, C is the capacitance associated with the charge store <b>120</b>, C_intis an internal capacitance <b>620</b> associated with the output driver <b>130</b>, and C_gsis a parasitic capacitance <b>640</b> associated with a driving transistor of the output driver <b>130</b>. In some embodiments, C=C_int+C_gs. Therefore, in these embodiments, the discharged voltage=V_on. Therefore, in some embodiments, the discharged voltage is different than the pre-turn-on voltage, for example. However, it will be appreciated that the pre-turn-on voltage is based on at least one of a turn on voltage (V_on) associated with the voltage provider <b>110</b>, a capacitance of the charge store <b>120</b>, an internal capacitance <b>620</b> of the output driver <b>130</b>, or a parasitic capacitance <b>640</b> of a driving transistor or third MOS transistor <b>610</b> of the output driver <b>130</b> in other embodiments.

p-0031In some embodiments, the method comprises charging the charge store to the pre-turn-on voltage based on a capacitance associated with the third MOS transistor of the output driver. Additionally, the method comprises connecting the charge store to the output driver based on the charge store charged to the pre-turn-on voltage. In other embodiments, the method comprises charging the charge store to the pre-turn-on voltage based on a first current source, such as the first current source <b>430</b> of <figref idrefs="DRAWINGS">FIG. 4</figref>.

p-0032<figref idrefs="DRAWINGS">FIG. 8</figref> is a schematic diagram of an example start-up circuit <b>800</b> for operating an output driver, according to some embodiments. For example, start-up circuit <b>800</b> comprises a voltage provider <b>110</b>, a charge store <b>120</b>, and an output driver <b>130</b>. In some embodiments, the voltage provider <b>110</b> is the voltage provider <b>110</b> of <figref idrefs="DRAWINGS">FIG. 4</figref>, the charge store <b>120</b> is the charge store <b>120</b> of <figref idrefs="DRAWINGS">FIG. 5</figref>, and the output driver <b>130</b> is the output driver <b>130</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>. It will be appreciated that in some embodiments, the voltage provider <b>110</b> comprises the second control switch <b>142</b>, while in other embodiments, the charge store <b>120</b> comprises the second control switch <b>142</b>. Additionally, in some embodiments, the output driver <b>130</b> comprises the first control switch <b>144</b> or the third control switch <b>146</b>. However, it will be appreciated that in other embodiments, the charge store <b>120</b> comprises the first control switch <b>144</b> or the third control switch <b>146</b>. In the start-up circuit <b>800</b>, the first control switch <b>144</b>, the second control switch <b>142</b>, and the third control switch <b>146</b> are open. However, it will be appreciated that in some embodiments, such as at a first time, the first control switch <b>144</b> is open, the second control switch <b>142</b> is closed, and the third control switch <b>146</b> is closed. Further, in other embodiments, such as at a second time, the first control switch <b>144</b> is closed, the second control switch <b>142</b> is open, and the third control switch <b>146</b> is open.

p-0033<figref idrefs="DRAWINGS">FIG. 9</figref> is a schematic diagram of an example start-up circuit <b>900</b> for operating an output driver, according to some embodiments. For example, start-up circuit <b>900</b> is associated with a first time when the first control switch <b>144</b> is open (not shown), the second control switch <b>142</b> is closed, and the third control switch <b>146</b> is closed. In this way, a first circuit <b>210</b> and a second circuit <b>220</b> are formed. For example, the first circuit comprises the voltage provider <b>110</b> of <figref idrefs="DRAWINGS">FIG. 4</figref> connected to the charge store <b>120</b> of <figref idrefs="DRAWINGS">FIG. 5</figref>. It is seen that, the second control switch <b>142</b> is closed to form a second connection at <b>142</b>. The first circuit <b>210</b> comprises a first current source <b>430</b>, a first MOS transistor <b>410</b>, a second MOS transistor <b>420</b>, and a capacitor <b>510</b>. The first MOS transistor <b>410</b> and the second MOS transistor <b>420</b> are associated with respective turn on or operating voltages (V_on). Therefore, the first current source is configured to charge the capacitor <b>510</b> to a pre-turn-on voltage=V=2*V_on. The second circuit <b>220</b> comprises the output driver <b>130</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>. In some embodiments, the third control switch <b>146</b> is connected to ground <b>106</b>, thus forming a third connection from a third gate of a third MOS transistor <b>610</b> to ground <b>106</b>. When the third gate of a third MOS transistor <b>610</b> is connected to ground <b>106</b>, the third gate is at a logic low voltage level, and the third MOS transistor <b>610</b> is off. Therefore, pad <b>108</b> remains at a logic high voltage level.

p-0034<figref idrefs="DRAWINGS">FIG. 10</figref> is a schematic diagram of an example start-up circuit <b>1000</b> for operating an output driver, according to some embodiments. For example, start-up circuit <b>1000</b> is associated with a second time when the first control switch <b>144</b> is closed, the second control switch <b>142</b> is open (not shown), and the third control switch <b>146</b> is open (not shown). In this way, a third circuit <b>310</b> and a fourth circuit <b>320</b> are formed. For example, the third circuit comprises the voltage provider <b>110</b> of <figref idrefs="DRAWINGS">FIG. 4</figref>. The fourth circuit <b>320</b> comprises the charge store <b>120</b> of <figref idrefs="DRAWINGS">FIG. 5</figref> connected to the output driver <b>130</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>. In some embodiments, the first control switch <b>144</b> is closed to form a first connection from the capacitor <b>510</b> of the charge store to a third gate of the third MOS transistor <b>610</b>. When the third gate of the third MOS transistor <b>610</b> is connected to the capacitor <b>510</b>, the third gate is immediately driven to a logic high level at least because the capacitor <b>510</b> is configured to discharge a stored voltage, such as a pre-turn-on voltage to the third gate of the third MOS transistor <b>610</b>. In some embodiments, the stored voltage is the pre-turn-on voltage and the voltage resulting from the discharge is different than the pre-turn-on voltage and is based on at least one of capacitance <b>510</b>, internal capacitance <b>620</b>, or parasitic capacitance <b>640</b>. Therefore, the third MOS transistor <b>610</b> is activated quickly and configured to immediately pull down pad <b>108</b>. When the third gate is at a logic high level, the third MOS transistor <b>610</b> is on, thus pulling a voltage level associated with pad <b>108</b> down to a logic low level, for example.

p-0035According to some aspects, a start-up circuit for operating an output driver is provided, comprising a voltage provider configured to charge a charge store to a pre-turn-on voltage. In some embodiments, the start-up circuit comprises an output driver comprising a first control switch configured to control a first connection between the charge store and the output driver.

p-0036According to some aspects, a method for starting an output driver is provided, comprising charging a charge store to a pre-turn-on voltage. In some embodiments, the method comprises connecting the charge store to an output driver to start the output driver.

p-0037According to some aspects, a start-up circuit for operating an output driver is provided, comprising a voltage provider configured to charge a charge store to a pre-turn-on voltage based on a second control switch configured to control a second connection between the voltage provider and the charge store. In some embodiments, the start-up circuit comprises an output driver comprising a first control switch configured to control a first connection between the charge store and the output driver and a third control switch configured to control a third connection between a gate of a metal oxide silicon (MOS) driving transistor and a ground.

p-0038Although the subject matter has been described in language specific to structural features or methodological acts, it is to be understood that the subject matter of the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

p-0039Various operations of embodiments are provided herein. The order in which some or all of the operations are described should not be construed as to imply that these operations are necessarily order dependent. Alternative ordering will be appreciated based on this description. Further, it will be understood that not all operations are necessarily present in each embodiment provided herein.

p-0040Moreover, “exemplary” is used herein to mean serving as an example, instance, illustration, etc., and not necessarily as advantageous. As used in this application, “or” is intended to mean an inclusive “or” rather than an exclusive “or”. In addition, “a” and “an” as used in this application are generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Also, at least one of A and B and/or the like generally means A or B or both A and B. Furthermore, to the extent that “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.

p-0041Also, although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur based on a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims.